US2870001A - Method of fluidization - Google Patents

Description

Slap/124702 Jan. 20, 1959 G. P. GIUSTI ET Al. 2,570,001

METHOD OF' FLUIDIZATION Filed June 26,` 1952 lINVENTORS divided form. v

J modied embodiment.

United States Patent METHOD OF FLUIDIZATION Gino P. Giusti, New Kensington, and Axel R. Johnson,

Pittsburgh, Pa., assiguors to Texas Guif Sulphur Company, New York, N. Y., a corporation of Texas Application June 26, 1952, Serial No. 295,746

5 Claims. (Cl. 75--9) This invention relates to a tluidization process involv`- ing a gas and an ore or other solid in which the gas may react chemically with the ore or other solid or may act physically on the ore or other solid.

l In the iluidization technique a minimum gas velocity ,is required to maintain the bed of solids in the desired uidized state.' This minimum gas velocity is a complex function of the properties of the fluidizing gas `andthe size and shape of the solidfbeing lluidized. For a given material higher gas velocity is required for a larger particle than for a smaller one.- Present practice inindustrial units is to supply the solids-at a maximum particle Vsize of 14 mesh because the use of particles of much larger size requires such high gas velocities, with attendant increased cost, ras to be uneconomical. Y That is due to the fact that a majorlcost item in av fluidization process is that ofy grinding the material tov a size amenable to lluidizay 2,870,001 y Patented Jan. 20,. 195s 2 disintegrable is fed to a lluidized bed in which the ore reacts chemically with the iluidizing gas with liberation of heat orV physically, due to the heat in the gases, giving otI gaseous products. Under the influence of heat within the fluidized bed the coarse ore particles disintegrate largely or wholly into particles ne enough for ready iluidization by the conventional gas velocities.

The importance of eliminating part of the grinding to tine particles becomes evident upon consideration of Ritl tengers Law, the validity of which, at least in the range `of small particle sizes, has been confirmed by the work f of the U. S. Bureau of Mines reported in its Bulletin 402. 'That law states that the work required for size reduction in grain is proportional to the new surface area formed. Assuming, for simplicity, that the particles being ground are spheres, `a plant grinding ore 5 inches in diameter to 1/2 inch diameter will use only abontzonehalf the power' required to reduce the same size feed to minus 14 mesh. Consequently it is clear that in the kpractice of this invention major savings are attained by t the abilityfto use a coarser feed than has been conventional.

Inthe practice of Vthis invention the coarse ore is fed,

say as 1/2 inch lumps, to a fluidized bed in a shaft having at its lower end a conduit of substantially smaller cross lsectional' area to which the lluidizing gas is supplied. The

-cross sectional area of the shaft and of its downwardly 'i i of.

rtion at anyeconomical gas velocity, i. e., the higher the the solid to readily liuidizable particle size, and that effects the desired result as readily and eciently as would be the case if the solid were` fed in the conventional finely A particular object is toprovide a method of treating p certain sulfur ores that disintegrate due tochemical or physical action under the inuence of heat while obtaining the advantages stated in the foregoing object.

v A further object is to providea method in accordance with the foregoing objects in which there is'exothermic chemical reaction between the solid and the fluidizing gas. y

A further Objectis to provide simplenapparatus for performing the method. n, Y --M V Other "objects will appear from thel following specifica- Y tion.

The invention willb'e described Withwreferernce to the accompanying drawingsin which'lig. l is a schematic representation of vone 'form of apparatus inaccordance v with and for practicing the method of the invention; and

Figi. 2 a fragmentary view similar to Fig. 1 showing a We have discovered, and itis upon this that our invention is in large part predicated, that in the uidization 50' products desired.

'i may be supplied by exothermic reaction betweenv the ore and the fluidizing gas or it may be supplied by burning a extending conduit are so related to each other and t'o the velocity of the gassupplied to the conduit that the velocity within the conduit is suicient to keep the bed linthe shaft but such that due to the increased cross sectional area in the shaft the consequent lowered velocity vsuthces to lluidize the bed. l

The large ore particles fed to the bed disintegrate, or

' shatter, upon contact' with `or moving through the bed Y due to heat in the iluidizedbed so that all, or substantially 1 all, lof the ore'fe'ed disintegrates into readily fluidized size.

Any material that does not so disintegrate -eventually reaches and leaves the bottom of the bed through the conduit yand s uch over-size material is withdrawn in any of ajvariety of ways. The disintegrated material, or cinder, is Ycontinuously withdrawn from theupper ysurface of the bed to maintain a substantiallyconstant upper bed levelf lDue to the retarded movement 'through the bed, such over-size particles will have been largely reacted before they drop from the bed. Likewise, product gasesare' withdrawn from the bed and treatedin--accordance with the reaction products and the ultimate In the practice ofthe invention the heat in-the bed combustible gas in the bed or vby tluidizing with'heated inert gas. vFor example, in the case of disintegrable sulfur oresuidizing with hot inert gas will elfect'the desired disintegration and at -the same time cause distillatiouof sulfur from the ore. Or,jvarious chemical reactions may n be accomplished, .asiby fluidzing with air under conditions to cause lcombustion of part or all o-f the .sulfur to sulfrfldioxide' with liberation ofthe `heat necessaryv. to cause physical disintegrationof the `coarse feed. ,Again, chlorine will react with elemental sulfur or sulfide sulfur in ores. Likewise, although the invention fis typified by v,and explained with reference to'certain sulfur ores,'it is Y applicable'likewise to other solids that disintegrate' under technique of conducting a process involving a gas and a solid, typified by an ore, an unusually coarse ore feed may be used where the ore is ofthe type that disintegrates upony being heated:A -More particularly, in the practice of i our invention such an orein theA form of lumps too large to be uidized practically andeconomically if not heat- ,the influence ofheatjor by reaction.

f.. v'The invention may be described in furtherdetail with ,"reference tothe accompanying drawings, Having'reference ,to Fig.'l there isl provided a'y shaft 1 for receivingfa fluidized bed 2Ld At` its lower end the shaft slopes downwardly substantially smaller cross sectional area than that of shaft 1. In this embodiment conduit 3 extends into a chamber 4. Gas for tluidizing is supplied to the chamber through a conduit S.

In accordance with the inventionl the gasis supplied at a velocity Ysuch as to be great enough in conduit 3 to maintain the uidized bed 2 within the shaft, thus eliminating the bed plate that supports the lluidized bed in conventional fluidizing apparatus and which would, if used permit the build up of over-size solids and eventually halt uidization. In other words, the shaft is freely open to its downward continuation portions.

For most purposes the cross sectional area of conduit 3 is but a fraction of that ofthe shaft 1, its exact area being dependent upon the velocity of the gas passing upwardlythrough itV and the character and depth of the bed so-as to hold the bed within the shaft but at the same time so that the velocity of the gas when it expands into the shaft, and thusows at a lower velocity, will uidize the bed. Preferably the relations are such that, for many purposes, the velocity in the bed is from 0.5 to 2.0 feet per second. For most purposes it is preferred that the velocity within the shaft shall be below the minimum carry-over velocity of the bed and treated ore, or cinder, particles although if desired for any reason it can be such as to cause complete, or substantially complete, carry-over of cinder with the product gases.

The ore is fed continuously to shaft 1, as by appropriate feeding means, not shown, to a conduit 6 so that the coarse particles fall to the upper surface of bed 2. In accordance with the invention the ore feed contains particles so coarse, e. g., one-half inch lumps, as to be not uidizable under the gas velocities normally used in fluidizing, e. g., 0.5 to 2.0 feet per second. As the ore enters the bed it becomes heated and disintegrates into sizes adapted to fluidization, say 14 mesh or liner. The treated ore is removed to maintain the upper bed level by any suitable means, as by means of an over flow 7. Product gases are withdrawn from the top of the shaft through a conduit 8 and treated according to the operation being conducted.

Any coarse ore particles that are not disintegrated to iluidizable size will eventually work to the bottom of the bed under the fluidizing action and will fall through conduit 3 into chamber 4 from which they may be removed periodically or continuously by the use of any suitable valving means 9 that does not interfere with the uidizing.

The invention is particularly applicable to the treatment of certain sulfur ores that are found in surface deposits in Peru and Chile and which, when dropped into a bed supplied with air, will under the resultant combustion fall-apart into particles readily uidizable, leaving only about 10 percent, and not more than about 2,0 percent, of the feed in lumps too large for uidization. Such ores carry sulfur mechanically rather than chemically bound, ,and usually they are of siliceous nature. In

other words, in such ores the sulfur is free as contrasted with that in pyrites. Alternatively, these same ores will disintegrate when dropped into'a bed supplied with a burning `gas or with hot, inert gases.

In the bed, assuming air as the fluidizing gas, at least someof the sulfur of the ore will be burned to,.sulfur dioxide, and the product gases composed of sulfur vapor, sulfur` dioxide and nitrogen, are withdrawn and treated to recover the sulfur and possibly the sulfur dioxide, which may be recovered as suchor used for the production of elemental sulfur. If the fluidizing gas in either a burning gaseous fuel or hot, inert gases, then the product gases composed of sulfur vapor and inert constituents are withdrawn and treated to recovery the sulfur. Depending upon the ore and upon the conditions within the bed, such kas volurnepof air feed, the product gases lmay contain sulfur dioxide and no' sulfur vapor. c A v InV starting up a bed, ore of minus 14 mesh may rst be supplied to form an original bed that is uidized by air to supply heat, or by other gas, the main purpose being to bring the bed to a temperature suicient to cause disintegration of coarse particles as charged and to be able to continue operation in this manner. When the bed has reached the proper temperature the feed of fine material is discontinued and thereafter the ore is fed in the coarse form characteristic of this invention. Alternatively, if desired for any purpose, the bed may be ".1 formed initially from an inert material that is brought to neat in any desired way, as by means of gas burners, after which the coarse ore feed is initiated and continued. Various inert `materialsmay used for this purpose, an example being tirebriclr of 20 x 60 mesh size.

The embodiment shown in Fig. 2 differs from that of Fig. 1 in that the liuidizing gas is supplied through a conduit 5a directly to the conduit 3a that extends downwardly from the shaft 1a, and at its lower end the conduit 3a opens into a collecting chamber 10 from which the accumulatedV over-size particles are withdrawn through suitable valving means 9a.

Although in the embodiments shown the ore is fed above the surface .of the fluidized bed, it will be understood that it can likewise he fed directly into the bed, e. g., laterally or sub-surface.

In view of what hasvbeen said the term reacting as used in the claims is to be taken to include both true chemical reaction accompanied by disintegration to smaller lparticle size as well' as the physical reaction of disintegration unaccompanied by chemical action. Likewise, the term "ore is used to refer to solids that are disintegrable by heat or by reaction.

According to the provisions of the patent statutes, we have explained the principle. of our invention and have illustrated anddescribed what we now consider to represent its best embodiment. However, we desirevto have it understood that, within the scope of the appended claims, the invention maybe practiced otherwise than as speciiically illustrated and described.4

Weclaim:

1. In a fluid bed method of reacting a gas and an ore, the steps comprising providing said bed in a shaft freely open to a downwardly extending continuation of substantially smaller cross sectional area that is freely open to a receiving chamber, continuously passing gas reactive with said ore into said continuation at a velocity therein to maintain said bed in said shaft but by the resultant decreased velocity upon entering the shaft to liuidize the bed, continuously feeding `to said bed ore disintegrable by heat in the form of lumps too large to be fluidized and supplyingheat in the bed to disintegrate such lumps into particlesY of uidizable size, any oversize ore as it reaches said' continuation falling freely through it, against the upflow of, said gas therein, into said chamber, withdrawing oversize material from said chamber, withdrawing treated ore of uidizable size from the upper end `of said bed, and withdrawing gases from thelbed.

2. A method according to claim 1 .in which the said bed is fluidized below the minimum carry-over velocity of the treated ore.

3. A ymethod according to claiml in whichsaid ore is a sulfur ore, and said gas is air.

4.v A methodaccording to claim 1 in which the heat in the bed Vis supplied by reaction between the ore and the gas.v

5. A method according to claim 4 in which the ore is p a sulfur ore carrying mechanically boundv sulfur, and the gas. is air.

(Otherreferences on following page) 5 UNITED STATES PATENTS Lykken Feb. 3, 1931 Chesler Mar. 30, 1943 Garbo Aug. 16, 1949 F Rollman May 1, 1951 l Matheson July 24, 1951 Thomas July 8, 19,52 Cyr et al. Dec. 9, 1952 Tarr et a1. Aug. 25, 1953 6 FOREIGN PATENTS Great Britain Apr. 6, 1948 OTHER REFERENCES

Claims (1)

1. IN A FLUID BED METHOD OF REACTING A GAS AND AN ORE, THE STEPS COMPRISING PROVIDING SAID BED IN A SHAFT FREELY OPEN TO A DOWNWARDLY EXTENDING CONTINUATION OF SUBSTANTIALLY SMALLER CROSS SECTIONAL AREA THAT IS FREELY OPEN TO A RECEIVING CHAMBER, CONTINUOUSLY PASSING GAS REACTIVE WITH SAID ORE INTO SAID CONTINUATION AT A VELOCITY THEREIN TO MAINTAIN SAID BED IN SAID SHAFT BUT BY THE RESULTANT DECREASED VELOCITY UPON ENTERING THE SHAFT TO FLUIDIZE THE BED, CONTINUOUSLY FEEDING TO SAID BED ORE DISINTEGRABLE BY HEAT IN THE FORM OF LUMPS TOO LARGE TO BE FLUIDIZED AND SUPPLYING HEAT IN THE BED TO DISINTEGRATE SUCH LUMPS INTO PARTICLES OF FLUIDIZABLE SIZE, ANY OVERSIZE ORE AS IT REACHES SAID CONTINUATION FALLING FREELY THROUGH IT, AGAINST THE UPFLOW OF SAID GAS THEREIN, INTO SAID CHAMBER, WITHDRAWING OVERSIZE MATERIAL FROM SAIDCHAMBER, WITHDRAWING TREATED ORE OF FLUIDIZABLE SIZE FROM THE UPPER END OF SAID BED, AND WITHDRAWING GASES FROM THE BED.

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